Clad pyrotechnics



Sept- 1968 T. Q. CICCONEETAL 3,401,636

GLAD PY'ROTECHNICS Filed Nov. 50, 1966 INVENTORS THOMAS Q. clccoNE WILLIAM E. PERKINS JAMES J. CAVEN ATTRNS United States Patent ce 3,401,636 CLAD PYROTECHNICS Thomas Q. Ciccone, Langhorne, Pa., William E. Perkins,

Runnemede, NJ., and James J. Caven, Philadelphia,

Pa., assiguors to the United States of America as represented by the Secretary of the Army Filed Nov. 30, 1966, Ser. No. 598,129 4 Claims. (Cl. 10287) ABSTRACT OF THE DISCLOSURE A clad pyrotechnic device for use in small cavity projectiles, such as flechettes, for example, which comprises a pyrotechnic composition enclosed in a metal sheath. The device is formed by filling the metal sheath which is plugged at one end with a pyrotechnic composition, then plugging the other end and passing the clad pyrotechnic through swaging and extruding means until desired diameters are obtained.

The present invention relates to clad pyrotechnics and more particularly to a method of charging small cavity projectiles with pyrotechnic compositions.

Pyrotechnic compositions are conventionally loaded into projectile cavities as powders in incremental loadings, employing extremely high tamping pressures of about 75,000 to 150,000 p.s.i. This method has proved to be economically feasible for cavities having dimensions from 0.180 inch diameter by 0.220 inch deep for caliber .22 to 0.325 inch diameter by 1.000 inch deep for caliber .50, and the intermediate sizes for small arms ammunition. However, the development of small arms projectiles smaller than caliber .22 and specifically those having cavities of or approaching 0.060 inch diameter by 0.750 inch deep has led to new problems in this field. These small cavity projectiles are extremely diflicult to load when using this method, and consequently are not potential production items.

Another factor of significance in the conventional method is the inherent tribochemical sensitivity of the pyrotechnic compositions. This sensitivity coupled with the numerous compressions required at high pressures, produced a rather dangerous situation resulting in an undesirable high percentage of premature actuations on the press.

It is the overall object of the present invention to provide a mass produceable metal clad pyrotechnic of proper diameter which can be handled facilely and loaded safely into a small cavity projectile.

Another object of the invention is to provide a metal clad pyrotechnic wherein the pyrotechnic is tightly packed and slow burning.

It is a further object of the invention to provide a metal clad pyrotechnic which produces an instantaneous or prolonged visible signal as required.

Additional objects will become apparent as this invention is more fully disclosed.

In order to fully illustrate the invention, reference is now made to the accompanying drawings showing the clad pyrotechnic employed in a typical small cavity projectile wherein:

FIG. 1 is a sectional view of a projectile embodying the clad pyrotechnic of our invention, and

FIG. 2 is a view of FIG. 1 along line 44.

Referring now to the drawings, a flechette projectile encases a clad pyrotechnic comprising a metal sheath 12 surrounding the pyrotechnic composition 13 disposed within a cavity of the projectile. Flechette 10 has the usual nose portion 14 and fins 15.

In accordance with the invention, a metal tube is first 3,401,636 Patented Sept. 17, 1968 plugged at one end and then filled with a standard pyrotechnic composition. After the second end is plugged, the tube is passed through a number of swaging and extruding means depending upon the original diameter of the tube, the final diameter desired and the metal sheath employed. A soft metal alloy, such as lead-antimony will require only 35 extrusions, while a hard metal, such as Inconel, may require up to 10 passes.

Various metallic sheaths and pyrotechnic compositions may be employed successfully in the instant invention. Among the successful metallic sheath materials are Inconel (a nickel base alloy containing about 15% chromium, about 6% iron and the balance being substantially nickel), zirconium (60% tin-40% lead), eutectic lead alloy, silver, aluminum alloys, and leadantimony alloys. All of these metals are compatible with the pyrotechnic composition, extrudable, and do not separate during flight. Standard pyrotechnic compositions which have been successfully employed are I-508 (14% magnesium, 78.5% barium peroxide, 5.5% Parlon, a

EXAMPLE I An eutectic lead (60% tin, and 40% lead) alloy tube of approximately inch outside diameter and /5 inch inside diameter is plugged at one end with lead or any suitable malleable metal and filled with I-508 pyrotechnic composition, and then plugged at the other end.

The tube is passed through swaging and extruding dies, the tube being reduced to an outside diameter of 0.060 inch with a sheath wall thickness of 0.001 inch. The pyrotechnic was tightly packed and had a core loading of about 20 grans per linear foot. The end plugs were cut away and lengths of the clad pyrotechnic were cut to fit the projectile cavity which had a diameter slightly larger than 0.060 inch. The clad pyrotechnic is then sealed in the cavity, preferably by inserting a beveled punch against the inside diameter of the sheath and exerting an outward force, thus forming a snug fit against the cavity wall.

The charged projectiles were evaluated in a night firing at the US. Coast Guard Firing Range and the ignited pyrotechnic could be seen at a distance of about 1,000 meters. The burning rates obtained from the sheath and pyrotechnic composition selected were from 1.0 to 2.0 inches per second.

It has also been discovered that the clad pyrotechnics of our invention had burning rates which were more reproduceable than those reported for standard pyrotechnic delay trains. Burning rates of A inch per second to 12 inches per second obtained with the clad pyrotechnic were easily reproduceable and were superior to standard delay trains.

The present invention has been described in detail. However as will be apparent to those skilled in the art, variations are possible without departing from the scope of the invention.

We claim:

1. A clad pyrotechnic device for use in projectile cavities smaller than about caliber .22 including a pyrotechnic composition, said composition being core loaded to about 20 grains per foot and comprising a 60% tin- 40% lead eutectic lead alloy sheath having an outside diameter of about 0.06 inch surrounding said pyrotechnic composition.

2. A method of charging pyrotechnic compositions into projectile cavities smaller than that about caliber .22 comprising the steps of plugging one end of a metal tube with a malleable metal,

filling said metal tube with a pyrotechnic composition,

plugging the open end with a malleable metal to form a clad pyrotechnic,

passing said clad pyrotechnic through swaging and extruding means until proper outside diameter of said clad pyrotechnic is obtained,

cutting said swaged and extruded clad pyrotechnic to fit length of said projectile cavity,

placing said cut clad pyrotechnic in said cavity.

3. The method as described in claim 2, wherein said metal tube is a nickel base alloy containing about 15% 5 alloy.

References Cited UNITED STATES PATENTS Clay l0287 Stevenson l0287 X Andrew et al. l0227 Smith 102-27 Null et al.

Stadler et a1 l0287 15 ROBERT F. STAHL, Primary Examiner. 

